1. Field of the Invention
The present invention relates to galvanic cells, and, in particular, to galvanic cells that comprise (a) an anode gel comprising mercury-free zinc powder, (b) an alkaline electrolyte, and (c) a cathode material that is separated from the anode gel by a separator and comprises manganese dioxide.
2. Description of the Related Art
Batteries of the abovementioned type are known as alkaline manganese primary cells. Because, on the grounds of protection of the environment, mercury is no longer being added to zinc powder, the anode material of cells of the abovementioned type is subject to increased corrosion which manifests itself in a higher self-discharge and a corresponding gassing rate. Numerous earlier attempts have been made to avoid these negative effects. For example, the zinc used as zinc powder has been alloyed with the metals bismuth, indium, lead, aluminum, and calcium (see U.S. Pat. No. 5,209,995). It is also known for the anode gel to be admixed with inorganic gassing inhibitors such as barium hydroxide (see U.S. Pat. No. 4,418,130). EP-A 582293 additionally discloses the addition of an indium salt to the electrolyte.
A further reduction of the gassing rate is desirable on the grounds of cost and with a view to improving the discharge behavior and increasing the capacity of the cells.
It is an object of the invention to provide a solution to the abovementioned problems.
Further aspects and advantages of this invention will become apparent from the detailed description which follows.